1. Field
The following description relates to a method and an apparatus for channel mitigation using per-tone spreading in single carrier block transmissions.
2. Description of Related Art
Single carrier block transmission (SCBT) is an attractive technique for wireless communications. SCBT is becoming all the more important as evident in its adoption in emerging standards like IEEE 802.11ad in the form of single carrier frequency domain equalization (SC-FDE) and also in long term evolution (LTE) release 8 uplink in the form of single carrier frequency division multiple access (SC-FDMA). The advantages of SCBT are the simplified transmitter, transmit signal characteristics and performance enhancement capabilities at the receiver using non-linear equalization techniques.
The concept of sub-banding is developed for wide band systems in recent times. With this concept, power saving is achieved in ultra wide band (UWB) systems. Several technologies based on personal area networks (PANs) make use of this band for building applications that can achieve medium to high data communication rates. In the method of sub-banding, a given bandwidth of 500 MHz (or more) is divided equally into ‘N’ sub-bands. These ‘N’ sub-bands can be used for providing multiple users access to channel bandwidth, for increasing rates of data communication by using different sub-bands for transmitting different data streams and improving communication performance by using different sub-bands for transmitting a same data stream.
Further, the data transmitted in each of the sub-bands are combined with unique orthogonal codes prior to transmission. When data streams are transmitted to multiple users, orthogonal codes, unique to each user, are used. When different data streams are transmitted to a same user, the orthogonal codes which are unique to each of the different data streams are used. If the orthogonal codes are applied to a same data stream transmitted in all of the sub-bands, the codes act as spreading sequences for interference rejection. When the orthogonal codes are applied to different data streams transmitted in each of the sub-bands, they can be used for rejecting the sub-bands carrying a different data stream. The method of transmitting orthogonal codes along with the data streams also helps in reducing the complexity of receiver at the one or more user nodes.
In sub-band ultra wide band (S-UWB), the transmitting device includes a plurality of sub-band signal generators for generating a plurality of sub-band signals based on the determined parameters, where each of the plurality of sub-band signals includes modulated bit streams spread using spreading codes. Further, at the receiver side, a receiving device of a sub-band ultra-wide band (S-UWB) communication system includes an analogue front end for receiving an S-UWB signal including a plurality of sub-band signals from a transmitting device over a UWB channel, where each of the plurality of sub-band signals include modulated bit streams spread using spreading codes. The receiving device also includes a sampler for sampling the S-UWB signal at rate of the sub-band bandwidth. Moreover, the receiving device includes a de-spreader for de-spreading the sampled S-UWB signal by filtering the sampled S-UWB signal at a cut-off bandwidth equal to a bit stream modulated symbol rate.
A major power consuming block in wideband systems like 60 GHz and UWB is the analog to digital converter (ADC) at the receiver. Further, in wide band systems, there has been the problem of inferior peak to average power ratio (PAPR) characteristics. This is especially severe in wideband systems thus limiting the performance or communicating range of the system.